Signaling-circuit arrangement



P 23, 1931 w. HAHNEMANN 1,802,555

SIGNALING CIRCUIT ARRANGEMENT Filed March 24, 192'? Patented Apr. 28, 1931 VIIUNITEVDY STATES WALTER HAHNEMANN, F BERLIN-MARIENFELDE, GERMANY, ASSIGNOR, TO C. LORENZ AKTIENGESELLSCHAFT, 0F BEBLIN-TEMPELHOF, GERMANY PATENT QFFICE SIGNALING-CIRCUIT ARRANGEMENT Application filed March 24, 1927, Serial No. 178,076, and in Germany March 19, 1926.

An ap lication for this invention has been filed in ermany on March 19, 1926.

'The present invention relates to the elimination from alternating current electrical circuits of disturbing oscillations which appear in an undesirable manner, more particularly in high frequency circuits, in the form of'higher harmonics and side frequencies. For this purpose it has been proposed to use filter or trap circuits known too as acceptors and rejectors to eliminate oscillations of certain frequencies from or allow them to pass freely into distinct circuit paths. However, such arrangements possess certain drawbacks, in common with the generally usedmeans,such as the employment of one or more intermediate circuits, of a considerable'loss of energy in these auxiliary circuits combined with a lack of selectivity to eliminate effectively the desired oscillations only and not to weaken the oscillations actively to be employed for signaling purposes.

' As these latter circumstances are of paramount" importance, more particularly in the case of wireless transmitter and receiver 1nstallations, it is a prime object of the present invention to secure the desired elimination in an efiicient way on the one hand and to avoid the above mentioned drawbacks of too great an energy loss in'theauxiliary circuits.

On the other hand the invention is more particularly concerned with an eliminating circuit arrangement containing a rejector circuit tuned to the frequency of the osc1lla tions to be actively employed forsignaling purposes and acting as a by-pass for oscillations of frequencies other than this predetermined signaling frequency. As a rejector circuit presentsto the frequency to which it a is tuned a'very large and to all other frequencies only a comparatively small 1mpedance, the effect is obtained of the rejector circuit being rendered opaque for the signaling frequency and transparent to frequencies other than this signaling frequency, which latter are therefore prevented from entering the circuit parts actively employed for signa1ing. According to my invention. this effect is effectively augmented by employing a rejector circuit having a capacity as large and an inductance as small as possible and by connecting the rejector circuit carrying the disturbing oscillations at points at which the voltage is approximately the pure watt voltage of the fundamental or signaling oscillation, i. e., the voltage corresponding to the energy component of the current. The self-inductance thereby preferably consists of one winding only and in order to keep the damping of the whole rejector circuit very low its ohmic resistance is decreased to a slight amount by employing a plurality of wires connected in parallel.

In order that the invention may be clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, in which:-

Figure 1 shows for the purposes of comparison a known arrangement of apparatus, and

Figures 2 and 3 illustrate connections suitable for radio transmission in accordance with the present invention.

Figure 4 shows a structure of a self-inductanoe of small value as to be employed in accordance with my invention.

Referring first to Figure 1, 1 is a high frequency generator which, in addition to the fundamental oscillation and constituted by a capacity 2 and inductance 3, the said circuit being in its turn coupled to the in.- ductance 4 of a consumer or other circuit II (antenna circuit).

The high frequency generator 1 may consist of a system comprising a high frequency generator and one or more frequency multipliers connected in cascade. In a system of this nature it is a well known fact that on account of the process of multiplication there may be present frequencies adjacent to the operating frequency appearing as side bands to the operating frequency. In particular they may be apparent as variations in could be represented by a carrier frequency and two side bands, one slightly above, the other slightly below the operating frequency. It can be readily seen that this type of side bands requires very careful attention for elimination, which this invention accomplishes.

In order to keep the disturbing oscillations existing in the generator circuit I away from the circuit II, a rejector circuit, consisting of a parallel combination of inductance 5 and capacity 6 and tuned to the fundamental oscillation, is connected in parallel with the transmitting inductances According to my invention the capacity 'of the rejector combination is preferably made as large and the inductance as small as possible. To this end the inductance is made of a single turn or of only a few turns which, for the purpose of reducing its damping or ohmic resistance, may be made of a number of single conductors connected 111 parallel which may be twisted together, these conductors being either solid or in their turn constituted by strands for the purpose of further reduction of the losses.

In Figure 4 the structure of such an inductance is shown. A number of windings 8 connected in parallel of solid or stranded wire are arranged on an hexagonal frame structure, whose one face 1' is fixed on a support and whose other faces 26 are rendered movable by joints 7, so that for altering the self-inductance the effective area may be varied by means of a spindle 9 with a hand wheel 10'. All the wires are connected in parallel, so that on the one hand the self inductance is kept very low and on the other hand the ohmic resistance or the damping reduced to a minimum value. The spindle 9 is supported by a bracket 11.

The action is then such that the fundamental oscillation passes almost exclusively through the coil 3 (Figure 1) and is transmitted to the circuit II, whilst in the case of disturbing oscillations, those of a higher frequency find a short circuit or shunt path in the large capacity 6 and those of lower frequency in the comparatively small inductance 5.

The rejector circuit situated between the points A and B receives only the watt current of the fundamental oscillation which is in inverse ratio to the damping of the rejector circuit and the power consumed in this circuit will be the greater, the greater the voltage at its terminals A and B. The smallest voltage appearing in the circuit 1, 2 and 3 is the pure watt voltage, that is the voltage corresponding to the pure en ergy component of the current in the circuit, and according to a further feature of the inventionthe rejector circuit 5, 6 is connected to the points at which there is, as far as possible, only pure watt voltage in respect of the fundamental oscillation as shown by Figure 2.

The connection shown in Figure 2 differs from that in Figure 1 by the addition of a condenser 7 The whole oscillatory circuit 1, 2, 7, 3 is subdivided here in such a manner as to obtain at the points A and B as far as possible the pure watt voltage for the fundamental oscillation. In this case the machine 1 which is assumed to represent an inductive resistance and the condenser 2 must be in resonance with the fundamental or signaling wave, also the inductance 3 and condenser 7 so that in fact at the points A and B, there will be the smallest possible voltage, that is to say the watt voltage. The rejector circuit 5,6 could also be considered as a coupling circuit, in which case the circuit 1, 2 represents the primary tuned oscillation'circuit and the circuit 3, 7 the second-.;.

ary tuned oscillation circuit; the rejector circuit then offers the greatest resistance to the fundamental oscillation, that is to say the coupling in respect of the latter is exceedingly tight, whilst the disturbing -oscil-.

lations are short circuited by the inductance 5 or capacity 6, which act as a loose "coupling in respect of them.

Figure 3 shows the application of the connection to an aerial circuit; in this case.

the inductance 4 and the capacity 8 represent one partial oscillation circuit, and the aerial load coil 9 and the-capacity of the aerial 10 with respect to the earth 11, the

other partial oscillation circuit, whilst the.

inductance 5 with the capacity 6 connected in parallel with it, constitute the rejector circuit connected to the points A and B at which the pure watt voltage for the fundamental oscillation exists. Owing to the connection of the rejector circuit to points which carry as far as possible only the watt voltage and to the corresponding arrangement of the oscillation circuits in question, on the one hand the losses in the rejector circuit are reduced to a minimum, and on the other hand the best possible distribution of the disturbing oscillations takes place, more particularly when side frequencies situated on both sides of the fundamental oscillation are involved.

What I claim to be secured by Letters Patent in the United States is: I

1. In a circuit arrangement for filtering out a definite frequency from a spectrum or band of frequencies, a series tuned circuit branch consisting of an inductance and of a capacity in series for receiving input currents, a second series tuned circuit consisting of an inductance and a capacity in series for conducting output currents and a tuned circuit comprising a capacity and a single turn inductance connected in parallel said capacity being comparatively large and said single turn inductance oomparrtively small, means for tuning said three circuits to the 0 crating frequency substantially indepen ently of each other and means for conductively connecting said three circuits in parallel with each other.

2. In a circuit arrangement for filtering out a definite frequency from a spectrum or band of frequencies, a tuned input circuit comprising an inductance and a capacity connected in series, a tuned output circuit comprising an inductance and a capacity connected in series, a tuned intermediate circuit comprising an inductance and a capacity connected in parallel, means for conductively connecting said input, output and intermediate circuits in parallel, said inductance in said intermediate circuit consisting of a plurality of single turns connected in parallel whereby to reduce its resistance to a minimum, said capacity in said intermediate circuit being comparatively large, and means for tuning said three circuits to the operating frequency substantially independently of each other.

In testimony whereof I have afiixed my signature.

WALTER HAHNEMANN. 

